This invention relates to an apparatus for applying an adhesive web longitudinally and with U-shaped section about the edge of a panel or the like shaped part of sheet metal, which apparatus is equipped with web-guiding means comprising a funnel-like pre-folding channel, a pair of feed and press-on rollers each of which rollers comprises a feed roller shaft being spring-biassed to press one roller against the other, said two feed and press-on rollers being adapted for receiving between them a pre-folded adhesive web emerging from said pre-folding channel and for pressing said pre-folded adhesive web against an edge and against opposite sides adjacent said edge, of a panel or the like shaped part of sheet metal, while said part is being introduced into contact with said folded adhesive web.
In sheet metal-processing industries, pressure- or heat-hardenable adhesive tapes are widely used to paste over folded seams connecting metal parts with each other. Thus, it is customary in the automobile industry to seal in this manner folded seams of certain automobile body parts, in particular doors, and thereby to avoid the danger of corrosion.
In the automobile industry and similar branches of industry, there are usually employed adhesives in liquid or pasty form for producing such pasted-over folded seam joints, which adhesives are applied to the sheet metal parts to be joined in the form of a cord. This method of applying adhesive is unsatisfactory in several respects. One such drawback is seen in the fact that the distribution of the adhesive, attained by this method, over the entire folded seam is not sufficiently uniform, which fact may cause problems of corrosion, and, as another drawback, the use of adhesives in liquid or pasty form always causes problems of work hygiene.
In the manufacture of cans for preserving food and the like, it is also conventional to paste over folded seams or seal them with adhesives, by methods described, for instance, in U.S. Pat. No. 3,125,056, French patent application Publication No. 2,252,147 or Belgian Pat. No. 444,014. The adhesive is applied in these cases to the crimped edges of the parts of the can body being connected with one another, either in liquid or pasty form, by extrusion or like methods, in the form of strips of an adhesive tape.
Adhesives such as Araldit or Redux adhesives marketed by Ciba-Geigy AG, Basel, Switzerland, in the shape of foils or webs, are increasingly used, especially because of their advantages of safe applicability, satisfying the demands of work hygiene. However, in the past, such adhesive foils or tapes have only found very limited use, or no use at all, for sealing or pasting-over folded seams, e.g., of automobile body parts.
This is due to the fact that these adhesive webs are highly cohesively plastic (of high viscosity) and that their low tensile strength causes considerable difficulties in applying them mechanically. Additional complications arise when such strips of adhesive foils must be applied to parts of automobile bodies whose folded seams have a complicated configuration, in particular one that is curved tridimensionally. These difficulties are especially great when a crimped rim is to be provided with adhesive on both sides thereof, i.e. when the adhesive web is to be laid about the rim with a U-shaped web cross-section.
The hitherto known apparatus of the initially described type are only suitable for processing relatively stiff adhesive tapes of considerable tensile strength. This is, for instance, the case of an apparatus described in U.S. Pat. No. 4,155,798 which comprises a pre-folding channel and press-on rollers. Adhesive webs which, in contrast to adhesive tapes, must be applied after separation from a carrier web or tape, cannot be applied successfully in this and other known apparatus.
The known apparatus of the type described in U.S. Pat. No. 4,155,798 comprise free-wheeling press-on rollers. In other apparatus, especially those of the type in which Bristol board and the like drawing paper is to be provided with a border of adhesive tapes, these press-on rollers are rigidly coupled with a driving motor.